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The child participants of an Iron Man costume challenge got a surprise visit from the real Tony Stark at Comic-Con on Saturday.

"It took everyone a while to catch on, but the audiences have been driving the direction that movies go in for quite some time now," said Robert Downey Jr., who answered questions by fans both young and not-so young over the weekend. "And I think that Comic-Con is just a stark reminder that -- fans first."

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While the plot of the third Iron Man installation has remained under wraps, RDJ hinted that the story will delve deeper into the relationship between Tony Stark/Iron Man and Rhodey/War Machine.

"I feel that Rhodey and Tony had not entirely been explored as much as they might be," RDJ said. "And that -- in the comics -- was always a big part of it, and -- to me -- some of the heart of what was great about it."

Some of the biggest questions came in the smallest packages. One young fan asked, "How does it feel to be a hero in all the movies?"

"It's an odd thing," RDJ answered with a smile. "I take it as seriously as Shakespeare."

Iron Man 3 is set to release May 3, 2013.